A transportation network is any navigable system of roads, pedestrian walkways, paths, rivers, shipping lanes or other network that is utilized to transport humans or vehicles. A transportation network can also include combinations of routes for the above modes of transportation. These combinations of routes are referred to as multimodal transportation networks.
A transportation network can be modelled and stored as a digital representation in a digital map database. In so doing, the transportation network is usually represented as a plurality of navigable segments (or “links”) connected at nodes, with attributes being associated with the links and/or nodes. Nodes are therefore connectors between the links, and generally occur at intersections where there is a decision point with respect to travel from one navigable segment to another. Conventionally, in the context of a transportation network, the attributes limit how travel can flow on the network. For example, attribution may include: geometry, speed of travel, whether or not a turn at an intersection is allowed (i.e. allowable “maneuvers”), at least one direction of traffic flow, number of lanes, etc.
Typically, such digital maps of transportation networks are created by traversing all paths/elements of the transportation network with highly specialized location measuring and recording systems designed for this purpose. Transportation network information can also be gleaned from aerial images or compiled from existing localized digital transportation networks. It is also becoming more common to create, or at least update and/or refine, a digital map utilizing positional information representative of the movements of one or more, although typically a plurality of, location-aware mobile devices over the transportation network over time.
Such positional information is commonly referred to as “probe data” (or “probe traces”). Each trace indicates a geographic position of each mobile device against time, i.e. traces the path of the device. A location-aware mobile device, herein referred to simply as a mobile device, is any device capable of determining its geographic location from wirelessly received signals. The received signals may include signals received from satellites of a global navigation satellite system (GNSS), such as GPS signals. The mobile device may be a navigation device such as a portable navigation device (PND), in-vehicle navigation device, mobile phone, portable computing device, vehicle tracking device, and the like. The mobile devices may therefore be associated with a vehicle, but it is also envisaged that the mobile devices could be associated with pedestrians. The navigation device is arranged to record a trace of a path or route followed by the navigation device. The navigation device may store the trace in a local memory of the navigation device or may communicate the trace to a server computer, such as via a wireless data connection with the server computer. The trace may be formed from data indicative of a series of geographic locations at which the navigation device is located at periodic intervals. However in other embodiments the trace may be formed by data representing one or more curves indicative of the path of the navigation device.
Methods of creating, updating and/or refining digital maps using probe data may utilize probe traces as received from the mobile devices (often referred to as “uncoordinated” traces), refined probe traces (i.e. uncoordinated probe traces that have been subjected to one or more of the following: smoothing; adjusting the position of at least portions of the trace depending on the direction of traffic flow, filtering traces not associated with a type of the transportation network), one or more bundles each comprising a plurality of traces, or any combination thereof. Bundles of probe traces are formed from a plurality of individual probe traces, uncoordinated or refined, which traverse a path having the same beginning and at least one common divergence point within a spatial threshold value and which do not deviate, in location, by more than a threshold from a reference probe trace (e.g. a probe trace passing through a densely populated area of probe traces). In other words, a probe trace bundle is a single probe trace that represents a plurality of individual probe traces; and may be used beneficially in the creation, updating and/or refinement of a digital map.
Additional transportation network information, such as points of interest (POIs) are often analyzed via tabular information, for example, as via manual research; via directories of restaurants in a chain with their addresses; points supplied by customers, third parties, address lists, and the like, wherein the points of interest are assigned a coordinate (latitude/longitude) and/or geocoded. Unfortunately, the results can be fraught with errors, such as due to human error. Further, rating of the POIs is typically manual, and thus, generally proves, difficult and costly. In addition, the manual data gathered can become dated in a relatively short period of time, thereby rendering the data obsolete and increasingly inaccurate.